Full waveform refraction imaging of the regolith with the CIG stack

Full waveform refraction imaging with the common intercept gather (CIG) is a simple application of the stacking procedures routinely employed with seismic reflection data processing to the standard intercept time method. Accordingly, the stacked full waveform CIG is the refraction equivalent of the CMP stack with reflection methods. The CIG recasts the processing of refraction data into a format which is analogous to standard reflection data processing methodology. Stacking with the CIG addresses the two most important challenges with near surface refraction seismology. It significantly improves the signal-to-noise ratios of both P- and S-wave images (and therefore, the time models) of the base of the weathering, and it enables the convenient investigation of the head wave coefficient. The CIG can be stacked on either common receiver gathers or common shot gathers. As a result, the CIG exhibits the unique ability to separate the refraction signal into the up-going and down-going components. The stacked CIG waveforms approximate time model shifted versions of the source and receiver functions.